Turbofan gas turbine engines may have disruptions in the flow through the bypass duct, such as may be caused by accessories that project into the bypass duct flow path. These accessories encounter the airflow in the bypass duct and thus form partial obstructions to the bypass airflow through the bypass duct. The obstruction of the airflow by these accessories can cause static back pressure in the bypass air flow. This static back pressure may cause vibratory stress on the upstream stationary stators of the fan, and on the fan itself.